Many industries have need for the making of accurate temperature measurements utilizing pluralities of thermocouples. A key source of temperature measurement error in such systems, however, is the temperature difference between any of the cold junction thermocouple connections and a cold Junction reference sensor. The UTR apparatus is designed to increase the thermal conduction path between the cold junctions of the plurality of thermocouples and the cold junction reference, while preserving electrical isolation between these points.
To attain such electrical isolation but with thermal connection, various techniques have been earlier employed including those embodied in the Model UTR-48N and the DIG14 Model V2222 of the assignee of the present application, as described, for example, in the Kaye Product Data Sheet #506, Thermocouple Reference Systems and Data Sheet #500. In the aluminum frame carrying the epoxy-mounted matrix of heavy copper terminals of such apparatus, BeO ceramic wafers, metalized only on their two faces, are soldered between the copper terminals to form the matrix, with the ceramic body of the wafers providing excellent electrical isolation between terminals; and, because of the excellent thermal conductivity of such ceramic (approaching that of the aluminum frame), provides superior thermal coupling between terminals necessary to attain the desired uniform thermal reference function. As a result, the thermocouple reference junctions of all channels on the UTR plate are maintained at the same temperature, and one sensor, as before-described, may be employed to monitor the entire isothermal plate. A foam-filled enclosure thermally isolates the UTR terminal plate from ambient temperature changes, so that the response to a change in ambient temperature is extremely slow.
Multiple units, indeed, may be ganged together, if desired, to accomodate for any number of channels, and the UTR apparatus may be operated as shielded or unshielded units.
The construction required for the above and other previous UTR assemblies, however, has rendered such devices relatively expensive to manufacture, and quite specialized in components and assembly.
In accordance with the present invention, on the other hand, a novel UTR design has been evolved which is suitable for use with modular screw-terminal blocks, while obviating the need for ceramic wafers and the like, and with attendant lower cost manufacture and assembly (including by the end user), and with a higher degree of accuracy from close thermal contact of each UTR member with the associated cold junction and with shortened thermal paths.